Safety device for hydraulically operated lift

ABSTRACT

The device is shown as associated in the usual subfloor pit with a conventional hydraulically powered lift mechanism to loss or substantial droppage of the hydraulic pressure correspondingly depressurizes the safety cylinder unit, enabling its built-in housing is mounted atop the lift&#39;&#39;s power cylinder superstructure; and a pivotal, bifurcated arm or fork-shaped actuator head embraces the fixed housing, an operating extension tail of said head projecting from one side of the latter. The furcations of said pivoted head carry trunnion-like actuator pins, which extend through vertically elongated slots in opposite sides of the fixed housing; and the ends of said trunnions are received in outer side openings of each of a pair of identical collets. These are actuable in the fixed housing parallel to the axis of the lift&#39;&#39;s hydraulic power rod or piston for releasable frictional radial engagement with said rod of arcuate inner collet areas, thus to safety-halt an undesired downward retrograde movement of the latter. To this end external tapered collet wedge surfaces engage correspondingly tapered internal wedge surfaces of the fixed housing. The same source of hydraulic power which operates the lift rod is at all times in communication with a spring return-type safety cylinder unit of the device; and the plunger of this unit is connected to the extension tail of the pivotal actuator head. This is in a manner such that normal hydraulic pressure urges the head in a direction to de-wedge the collets from clamping engagement with the lift power rod, through the agency of the head&#39;&#39;s trunnions. A LOSS OR SUBSTANTIAL DROPPAGE OF THE HYDRAULIC PRESSURE CPRRES PMDOMG:U DE RESSIROZES THE SAFETY CYLINDER UNIT, ENABLING ITS BUILT-in return spring to operate the actuator head in the opposite direction and cause the collet members to grip the power rod against fall. Supplemental spring means normally assist in insuring separation of the collets from the rod when the device is not in operation.

United States Patent Kerr [ SAFETY DEVICE FOR HYDRAULICALLY OPERATEDLIFT [76] Inventor: James W; Kerr, 18232 Magnolia,

Southfield, Mich. 48075 [22] Filed: July 26, 1972 [21] Appl. No.:275,279

[52] US. Cl 187/8.45, 187/8.47, 92/15,

188/67, 91/41 [51] Int. Cl. B66f 7/00, Fl5b 15/26 [58] Field of Search187/845, 8.47;

[56] References Cited UNITED STATES PATENTS 3,096,075 7/1963 Brown188/67 3,695,144 10/1972 Goiffon 91/41 FOREIGN PATENTS OR APPLICATIONS1,103,862 6/1955 France ..187/8.47 697,244 9/1962 Italy 187/847 PrimaryExaminerRobert S. Ward, Jr. Attorney-Charles R. Rutherford powercylinder super-structure; and a pivotab braces the fixed housing, anoperating extension tail of said head. projecting from one sideof thelatter. The ufcations of said pivoted head carry trunnion-like actuatorpins, which extend through vertically elongated slots in opposite sidesof the fixed housing; and the ends of said trunnions are received inouter side openings of each of a pair of identical collets. These areactuable in the fixed housing parallel to the axis of the lift'shydraulic power rod or piston for releasable frictional radialengagement with said rod of arcuate inner collet areas, thus tosafety-halt an undesired downward retrograde movement of the latter. Tothis end external tapered collet wedge surfaces engage correspondinglytapered internal wedge surfaces of the fixed housing. The same source ofhydraulic power which operates the lift rod is at all times incommunication with a spring retum-type safety cylinder unit of thedevice; and the plunger of this unit is connected to the extension tailof the pivotal actuator head. This is in a manner such that normalhydraulic pressure urges the head in a direction to de-wedge the colletsfrom clamping engagement with the lift power rod, through the agency ofthe heads trunnions. A loss of substantial droppage of the hydraulicpressure correspondingly depressurizes the safety cylinder unit,

enabling its built-in return spring to operate the actuator head in theopposite direction and cause the collet members to grip the power rodagainst fall. Supplemental spring means normally assist in insuringseparation of the collets from the rod when the device is not inoperation.

13 Claims, 4 Drawing Figures PATENTEBJAN 8l974 3,783,976

sum 1 or 2 BACKGROUND OF THE INVENTION 1. Field of the Invention Thesafety device of the invention finds application in checking possibledangerous drop of hydraulic lifts or elevators of various types andsizes, for example, in sizes ranging from a use in a gas station repairspace up to installations servicing a considerable number of commercial,factory or residential building floors. The device will also have broadutility in other types of motion checking hydraulic or pneumaticpressure operated equipment, in any of which a positive mechanical checkof an accidental or emergency-occasioned retrograde movement of anobject is desired. This is in particular the case in an installation inwhich a simplicity of structure and quick, reliable fool-proof operationare essential. I

2. Description of the Prior Art A search has revealed the following US.Pats: Metz etaI No. 1,938,191,Dec. 5, 1933;

Stukenborg,No. 1,939,420, Dec. 12, 1933;

Ross et al., No. 3,088,546, May 7, 1963;

McAlpine, No. 3,094,192,.Iune 18, 1963;

Woor et al., No. 3,276,548, Oct. 4, 1966.

None of these relate, however, to a simple hydraulically controlledcollet-type safety checking mechanism for a lift or equivalent structurewhich is powered for emergency operation by the power source of saidstructure.

SUMMARY OF THE INVENTION The safety device of the invention, ashydraulically operated in the manner just mentioned by a very simplesafety cylinder unit, is otherwise mechanically of a very simple nature.In this respect the device comprises a pivotal actuator housing or headfulcrummed atop an upright post or standard for swing in a verticalplane including the axis of the lifts power rod, laterally outwardly toone side of which fulcrum, in relation to said rod an operating arm ofsaid head is pivotally articulated to the plunger of said safetycylinder, which is a very simple spring return type hydraulicallycoupled to the main fluid pressure power source.

That source normally urges the pivotal actuator head vertically in adirection to raise the two collets, as trunnion-carried on said head,and thereby normally maintain the collets out of wedged clampingengagement with the lift power rod. A failure or a substantial drop inhydraulic pressure on the rod instantly energizes the safety cylinderunit, with the result that the collets are driven down a very shortdistance to wedge the power rod to halt a drop of the latter in excessof, say 18 inches.

The effectiveness of the subject safety device is such that it willpositively clamp and hold the lift or elevator power rod even if all theoperating oil is drained from the latters cylinder, as in the event ofbursting ofa conduit. The device is capable of installation readily andexpeditiously in new or old installations; and its frictionalcollet-type rod locking operation does not externally score or damagethe power rod.

A simple spring means continuously acts between the collets to spreadthe latter, thus insuring against their freezing to prevent restorationof the safety device to normal. When the device has set for' lack ofpressure,

as contemplated, it will automatically self-release upon movement of themain power rod upwardly, after working pressure is restored, to theextent of only 1 inch. An attendant is not required to get into theelevator pit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a somewhat schematicsectional view through an ordinary elevator or lift pit, being in ageneral vertical plane including the axis of the power cylinder assemblyof the lift as equipped with the safety device of the invention;

FIG. 2 is an enlarged scale top plan view of said device, beingpartially broken away and in horizontal section on a line correspondingto broken line 2-2 of FIG. 3;

FIG. 3 is a side elevational view, also partially broken and in verticalsection along ine 3-3 of FIG. 2; and

FIG. 4 is a view in transverse vertical section on line 44 of FIG. 3,illustrating a detail of connection of an operating trunnion pin of thedevices actuator head with a releasable locking collet.

DESCRIPTION OF A PREFERRED EMBODIMENT FIG. I shows the generalorganization of parts of the safety device, generally designated 10, asassembled to a hydraulic lift or elevator structure 12, the latter beingtypically mounted at sub-floor level on the bottom of a pit 13. This pitis sized to receive an elevator or lift floor, platform, car track orequivalent support member 14 as raised and lowered by hydraulic powerstructure or unit 12. An external superstructure 15 of that unit, asfixedly connected thereto, bottoms on the floor of pit 13, to which itis bolted; and the units vertical sleeve extension 16 goes sufficientlydown in a vertical bore 17 of the pit to accommodate the most extendedposition, in that direction, of the elongated operator rod or piston 18of power unit 12. The latter is powered in cylinder structure 15 byhydraulic pressure oil admitted beneath a driven portion of piston '18,under control of a conventional reversing valve arrangement.

As also appears in FIG. 1, although better illustrated as to detail inFIGS. 2 and 3, the device 10 includes a fixed rectangular box like andopen-centered housing unit 20 which is welded at its bottom to alaterally projecting base plate 21, also open-centered, of substantialthickness. As thus composed, the housing 20 rests (FIGS. 1 and 3) atopthe superstructure l5 and is rigidly secured thereto by a seriesof studs22. Thus it is seen that the device 10 is adapted for ready installationon an existing cylinder assembly, as well as an equipment component ofan original installation.

Referring now to FIGS. 2, 3' and 4 in conjunction with FIG. 1, thesafety device 10 comprises a collet unit including a pair of identicallocking collets 24, each presenting a semi-cylindrical inner frictionallocking surface 25 to mate with an approximately equal peripheral areaof the power rod 18, which is shown as tubular in cross-section. Since(FIG. 3) the collets 24 are also of very substantial axial dimension,large friction areas are present at their rod mating surfaces 25 forreleasably locking rod 18 in the manner to be described.

Coil compression springs 26 seat in appropriate recesses 27 of thecollets 24, just diametrically outwardly of the latters lock surfaces25, said springs normally urging the collets for unfailing separation,but of course yielding to permit clamping under the control of theremaining parts of safety device 10.

Each of the collets has an external. frusto-conical wedging surface 29,which coacts with a correspondingly angled internal mating wedge surface30 on the fixed housing member 20', and the collets 24 are verticallyshiftable upwardly to release or disable such wed ging engagement, aswell as downwardly to restore it, under the control of actuator means ofdevice to be described.

Further in accordance with the invention, the fixed housing member isprovided with a pair of vertically elongated slots 32 which are indiametrically opposed relation to one another across the axis of powerpiston 18, as appears in FIG. 2, the slots 32 opening between the innerwedging surfaces of housing 20 and the latters upright external sidesurfaces 33. The latter, in conjunction with front and rear internalhousing surfaces 33', define the rectangular housing opening in whichcollets 24 are laterally confined. The housing base plate 21, of course,has a similar rectangular opening of smaller side-to-side widthsimilarly receiving and laterally confining the lower collet ends.

The fixed housing slots 32, as appears in FIGS. 1 and 2, are not only ofsubstantial vertical height, but also are sufficiently wide to receivewith generous lateral clearance 21 pair of actuator pin or trunnionmembers 34, which are fixedly carried by forked arms 35 of a movableactuator housing or head 36 of device 10, the operation of which islater detailed. For the time being, it suffices to say that thefurcation arms 35 have substantial lateral clearance relative to theupright sides 33 of fixed housing 20, and that their trunnion 34, asdiametrically opposed to one another in relation to the axis of rod 18,extend through the clearance slots 32. They have operative engagement attheir inner ends in side recesses 38 formed in the collets 24, saidrecesses inwardly terminating short of the wedging surfaces 25 of thecollet (FIG. 3).

FIG. 4 shows the recess 38 as receiving the actuator trunnion 34 withsubstantial horizontal clearance, thus accommodating a small arc ofswing of the trunnion as carried by pivotally mounted actuator arms 35,but with negligible vertical clearance, so'that lost motion issubstantially nil in the vertical shift of the collet 24 by the actuatorarm means.

The arms 35 are integrally connected in their forked relation to oneanother by a horizontal cross bar portion 40 of the head 36, whichportion in turn presents (FIGS. 1 and 2) a central, outwardly extendingactuator tail bar 41. This bar portion is journaled for vertical swingby a pivot pin 42 located approximately midway of the distance betweenactuator trunnion pins 34 and the free end of the tail 41; the pin beingcarried by a top clevis part 43 (FIG. 1) of an upright pedestal orstandard 44 supported on the floor of pit 13; and clevis 43 and pivot 42are at an elevation to bring the actuator head 36 in a substantiallyhorizontal plane when the safety device 10 is in a released position,with its collets 24 out of wedged checking engagement with rod 18.

This will be in a position of the collets somewhat above the location ofthe latter shown in FIG. 3, i.e., with the tops thereof thensubstantially co-planar with the top of fixed housing 28.

Adjacent its free end the actuator head tail 41 has a pivotalconnection, as at a' transverse pin 46, within'a second clevis part 47which is adjustably connected to the top of the plunger 48 of a springreturn-type hydraulic safety cylinder unit 49. The cylinder proper 50 ofsaid unit has a pivotal rockable connection at 51 to a top part of anupright standard 52 (FIG. 1) which, in common with the fulcrummingstandard 44, has a bolted connection, through a single base plate 53 forboth, to the floor of pit l3.

A fluid pressure L-fitting 54 operably connects an upper space of springreturn cylinder witha pressure line 55 appropriately connected forpressurization from the same source of hydraulic power (not shown) thatpowers the lift or elevator cylinder assembly 12 to elevate rod orpiston 18; such hydraulic connections for the safety cylinder unit 49and the cylinder 15 of unit 12 are simultaneously pressurized or not,the latter as in the event of a loss or substantial pre-determined andundesired droppage of pressure of hydraulic power oil.

Thus it is seen that in the normal non-emergency role of the device 10,its safety cylinder 50 will be pressurized to draw its plunger rod 48downward, as viewed in FIG. 1, with the result that the trunnionelements 34 on the arms 35 of its actuator head 36 are raised,correspondingly raising the collets 24 and dis-engaging the latterfrictional-wise from piston 18. The set of compression springs 26interposed between the collets insure this desired normal radial spacingof the collets relative to the rod. However, upon an emergency droppageof oil pressure beneath power piston 18, a corresponding pressuredroppage in safety cylinder unit 49 occurs, with the result that thelatters built-in return spring (not shown) instantaneously drivesplunger 48 and its connection to the tail 41 of actuator head 36upwardly, swinging the actuator head 36 counterclockwise as viewed inFIG. 1. This correspondingly moves trunnions 34 downwardly and causesthe wedging coaction of collet wedge surfaces 29 and. housing wedgesurfaces 30 (FIG. 3) to drive the collets radially for a strongfrictional clamping and motion-checking engagement with power piston 18.

What is claimed is: V

1. A safety device for a lift or like rodaxially powered operationallyunder fluid pressure in one direction but normally subject to retrogradeaxial movement in the event of a predetermined droppage of its fluidpressure operating power, said device being actuable to check saidretrograde movement and comprising collet-type means releasablyengageable with said rod to so check the latter, and means operativelyconnected to said checking means, being responsibly powered by thesource of fluid pressure operating power for said rod, to actuate saidsafety device in said event of operating power droppage, saidcollet-type checking means comprising a collet unit including a pair oflike collet members disposed radially outwardly of said fluidpressurepowered rod and movable radially inward to grip the latter, anda housing unit within which said collet members operate, said unitshaving coacting axially tapered wedging surfaces operatively engageablewith one another upon relative axial shift of said units to releasablyradially engage said collet members with said rod, and a single actuatorhead operatively connecting one of said units to said responsivelypowered means to effect said relative axial shift of said units, and anattendant radial shift of said collet members to grip said rod, in saidevent of fluid pressure operating power droppage.

2. The safety device of claim 1, in which said housing unit is a fixedone within which said collet members operate parallel to the operatingaxis .of said rod, said actuator head operatively connecting both ofsaid collet members to said responsively powered means to effect axialshift of said collet members in the housing unit.

3. The safety device of claim 2, in which said responsively poweredmeans comprises a fluid pressure cylinder unit having an elementoperated in one direction only under fluid pressure from said source,said element being operatively connected to said actuator head to effectsaid releasable checking engagement of said collet members with saidrod.

4. The safety device of claim 3, in which said operated element of saidcylinder unit is spring-returned in a direction opposite its directionof fluid pressure operation.

5. The safety device of claim 4, in which said operated element of saidcylinder unit has pivoted arm means operatively connecting the same withsaid actuator head and through said head with said collet members forsaid axial shift of the latter.

6. The safety device of claim 4, in which said arm means has trunnionelements extending through said fixed housing unit for operatingengagement with the respective collet members for said axial shift.

7. The safety device of claim 6, and further comprising means actingautomatically on said collet members to release them from checkingengagement with said rod upon restoration of fluid pressure operatingpower.

8. The safety device of claim 3, in which said operated element of saidcylinder unit has pivoted arm means operatively connecting the same withsaid actuator head and through said head with said collet members forsaid axial shift of the latter.

9. The safety device of claim 8, in which said arm means has trunnionelements extending through said fixed housing unit for operatingengagement with the respective collet members for said axial shift.

10. The safety device of claim 2, and further comprising means actingautomatically on said collet members to release them from checkingengagement with said rod upon restoration of fluid pressure operatingpower.

11. The safety device of claim 1, in which said responsively poweredmeans comprises a fluid pressure cylinder unit having an elementoperated in one direction only under fluid pressure from said source,said element being operatively connected to said actuator head to effectsaid releasable checking engagement of said collet members with saidrod.

12. The safety device of claim 11, in which said operated element ofsaid cylinder unit is spring-returned in a direction opposite itsdirection of fluid pressure operation.

13. The safety device of claim 1, and further comprising means actingautomatically on said one unit to cause a release of said collet membersfrom checking engagement with said rod upon restoration of fluidpressure operating power.

UNITED STATES PATENT AND TRADEMARK OFFICE Certificate Patent No.3,783,976 Patented January 8, 1974 James W. Kerr Application having beenmade by James W. Kerr, the inventor named in the patent aboveidentified, and Kingsley Corp., Brighton, Mich., a corp. of Mich., theassignee, for the issuance of a certificate under the provisions ofTitle 35, Section 256, of the United States Code, adding the name ofEdward S. Dyszer as a joint inventor, and a showing and proof of factssatisfying the requirements of the said section having been submitted,it is this 27th day of October 1981, certified that the name of the saidEdward S, Dyszer is hereby added to the said patent as a joint inventorwith the said James W. Kerr.

Fred W. Sherling Associate Solicitor.

1. A safety device for a lift or like rod axially powered operationallyunder fluid pressure in one direction but normally subject to retrogradeaxial movement in the event of a predetermined droppage of its fluidpressure operating power, said device being actuable to check saidretrograde movement and comprising collet-type means releasablyengageable with said rod to so check the latter, and means operativelyconnected to said checking means, being responsibly powered by thesource of fluid pressure operating power for said rod, to actuate saidsafety device in said event of operating power droppage, said collettypechecking means comprising a collet unit including a pair of like colletmembers disposed radially outwardly of said fluid pressure-powered rodand movable radially inward to grip the latter, and a housing unitwithin which said collet members operate, said units having coactingaxially tapered wedging surfaces operatively engageable with one anotherupon relative axial shift of said units to releasably radially engagesaid collet members with said rod, and a single actuator headoperatively connecting one of said units to said responsively poweredmeans to effect said relative axial shift of said units, anD anattendant radial shift of said collet members to grip said rod, in saidevent of fluid pressure operating power droppage.
 2. The safety deviceof claim 1, in which said housing unit is a fixed one within which saidcollet members operate parallel to the operating axis of said rod, saidactuator head operatively connecting both of said collet members to saidresponsively powered means to effect axial shift of said collet membersin the housing unit.
 3. The safety device of claim 2, in which saidresponsively powered means comprises a fluid pressure cylinder unithaving an element operated in one direction only under fluid pressurefrom said source, said element being operatively connected to saidactuator head to effect said releasable checking engagement of saidcollet members with said rod.
 4. The safety device of claim 3, in whichsaid operated element of said cylinder unit is spring-returned in adirection opposite its direction of fluid pressure operation.
 5. Thesafety device of claim 4, in which said operated element of saidcylinder unit has pivoted arm means operatively connecting the same withsaid actuator head and through said head with said collet members forsaid axial shift of the latter.
 6. The safety device of claim 4, inwhich said arm means has trunnion elements extending through said fixedhousing unit for operating engagement with the respective collet membersfor said axial shift.
 7. The safety device of claim 6, and furthercomprising means acting automatically on said collet members to releasethem from checking engagement with said rod upon restoration of fluidpressure operating power.
 8. The safety device of claim 3, in which saidoperated element of said cylinder unit has pivoted arm means operativelyconnecting the same with said actuator head and through said head withsaid collet members for said axial shift of the latter.
 9. The safetydevice of claim 8, in which said arm means has trunnion elementsextending through said fixed housing unit for operating engagement withthe respective collet members for said axial shift.
 10. The safetydevice of claim 2, and further comprising means acting automatically onsaid collet members to release them from checking engagement with saidrod upon restoration of fluid pressure operating power.
 11. The safetydevice of claim 1, in which said responsively powered means comprises afluid pressure cylinder unit having an element operated in one directiononly under fluid pressure from said source, said element beingoperatively connected to said actuator head to effect said releasablechecking engagement of said collet members with said rod.
 12. The safetydevice of claim 11, in which said operated element of said cylinder unitis spring-returned in a direction opposite its direction of fluidpressure operation.
 13. The safety device of claim 1, and furthercomprising means acting automatically on said one unit to cause arelease of said collet members from checking engagement with said rodupon restoration of fluid pressure operating power.